As you pointed out there are imbalanced ways of phrasing things and societal taboos that all lead to the imbalance of power where employers try to keep as much control as possible.

Not discussing salaries is the exact same thing - the employer doesn't want everyone to know how much their peers are making, lest it result in higher overall salaries. I always think of offering candy to a kid but saying "Don't tell anyone I gave you this". It's pretty clear someone is trying to be manipulative if they don't want anyone else to know the details of the deal.